Process for preparation of homogenous random partly crystalline copolymers of ethylene with other alpha-olefins

ABSTRACT

PREPARATION OF COPLYMERS OF ETHYLENE AND AN ALPHA OLEFIN HAVING A LEAST FOUR CARBON ATOMS USING AN INERT SOLVENT AND A CATALYST FORMED USING PARTICULAR RATIOS OF AN ALUMINUM HALIDE AND A VANADUM COMPOUND.

c. T. ELSTON 3,645,992 PROCESS FOR PREPARATION OF HOMOGENOUS RANDOMPARTLY Feb. 29, 1972 CRYSTALLINE COPOLYMERS OFETHYLENEWITH OTHERALPHA-OLEFINS 2 Sheetsfiheet 1 Filed Feb. 15, 1968 FEG.

COPOLYMERS \QTEROGENEOUS l COMONOMERS c B HOMOGENEOUS COPOLYMERS 1COPOLYMER MELTING POINT VS. 00MONOMER CONTENT mww 9. 5:: 02:3: 55 6660TOTAL CH I00 0. VINYL/ I00 0. COPOLYMER DENSITY VS. COMONOMER CONTENTPEG-Z I COMONOMER 2 c COPOLYMERS COPOLYMERS A HETEROGENEOUS BHOMOGENEOUS SIDE CHAIN CH I00 0.

INVENTOR CLAYTON T. ELSTON BY 5M0. W

ATTORNEY 2 1972 c. T. ELSTON PROCESS FOR PREPARATION OF HOMQGENOUSRANDOM PARTLY CRYSTALLINE COPOLYMERS OF ETHYLENEWITH OTHER ALPHA-OLEFINS2 Sheets-Sheet 2 Filed Feb. 15 1968 F I G- DENSITY connacnou FOR MELTINDEX GE: Ema 525960 DENSITY DIFFERENCE FROM MELT INDEX L0 INVENTORCLAYTON T. ELSTON ATTORNEY United States Patent US. Cl. 260-8058 13Claims ABSTRACT OF THE DISCLOSURE Preparation of copolymers of ethyleneand an alpha olefin having'at least four carbon atoms using an inertsolvent and a catalyst formed using particular ratios of an aluminumhalide and a vanadium compound.

The present invention relates to the controlled continuouscopolymerization of ethylene and one or more a-olefins to partlycrystalline homogeneous random c0- polymers of closely controlledphysical properties, and to the copolymers resulting therefrom.

' The copolymerization of ethylene and various a-olefins "(e.g. butene,hexene, octene, etc.) using a coordination catalyst system to yieldpartly crystalline copolymers with a range of physical properties iswell known and is described in Canadian Patent 664,211 issued toAnderson and Stamatoif on' June 4, 1963. The partly crystallinecopolymers so prepared have a density and a stiffness intermediatebetween those of a linear polyethylene homopolymer (0.96 g./cc., 140,000p.s.i) and a completely amorphous ethylene-a-olefin rubber (0.85 g./cc.,less than 5000 psi). These partly crystalline copolymers possessphysical properties which render them suitable for a wide range ofpractical applications such as film extrusion,

blow moulding, injection moulding, wire coating and paper coating. Thecopolymer composition and molecular weight are adjusted to the optimumvalue for the particular end use desired;

It has now been discovered that the physical properties of such partlycrystalline copolymers are dependent not only on their molecular weightdistribution and the amount and type of comonomer incorporated into thecopolymer but also upon the distribution of the comonomer units alongthe polymer backbone. It has further been discovered that such molecularweight and comonomer distribution can be controlled within desirablelimits by employing coordination catalysts having narrow and unforeseenranges of v composition.

. In theart, it is well known that within any given co- .polymermolecule, the comonomer distribution may be random, regular, block orcombinations thereof. The present invention is concerned mainly with thepreparation and properties of ethylene-a-olefin copolymers preparedin,.a constant environment reactor using coordination catalyst systems.

. However, the comonomer distribution between the molecules of thecopolymer must also be considered.

Upon consideration of the latter distribution factor, two classes ofcopolymers have been noted, namely hetero 'geneous copolymers andhomogeneous copolymers.

Heterogeneous copolymers may be defined as those in which the copolymermolecules do not have the same ethylene/comonomer ratio. Thesecopolymers can be differentiated into three basic types dependent uponthe degree of heterogeneity and whether the ethylene/comonomer ratio isa function of the size of the molecule. A heterogeneous copolymer (typeI) might be defined as one in which the ethylene/comonomer ratio is nota function of the size of the copolymer molecule, i.e. the comonomercontent of all the molecular weight fractions is the same but withineach such fraction, there are individual molecules with a comonomercontent above or below the average. Heterogeneous copolymers might alsobe defined as those in which the ethylene/comonomer ratio is a functionof the molecular weight, with type II copolymers being those in whichthe ratio increases with molecular weight and type III copolymers beingthose in which the ratio decreases with molecular weight. Combinationsof types I, II and III are also possible.

The preferred ethylene-a-olefin copolymers belong to the classdesignated as homogeneous. Homogeneous copolymers may be defined asthose in which not only is the comonomer randomly distributed within agiven molecule but all the copolymer molecules have the same ethylene/comonomer ratio. Homogeneous copolymers of narrow molecular Weightdistribution exhibit a reduced haze level in extruded film, higherimpact strength, reduced tendency towards delamination in extrudedarticles and better balance of physical properties in the machine andtransverse direction of extruded film when compared with conventionalheterogeneous copolymers.

These subtle but extremely important comonomer distribution featureshave not been considered in the prior art relating to partly crystallineethylene-a-olefin copolymers. It is only with the advent of newinstrumental techniques that studies of possible molecularconfigurations can be made. Previously, fractionation of a wholecopolymer into 10 to 20 sharp molecular fractions and subsequentcomonomer analysis of the individual fractions had been assumed to offerunequivocal proof of distributional homogeneity of the copolymer.However, a heterogeneous random copolymer (type I) would not show anycompositional heterogeneity under these conditions. Therefore, aconstant ethylene/comonomer ratio as determined by analysis of sharpmolecular weight fractions of a copolymer is a necessary but not asufficient condition for proof of copolymer homogeneity. An additionaland more reliable indication of copolymer homogeneity is therelationship between the crystalline melting point of the wholecopolymer (or sharp molecular weight fraction) and its comonomercontent.

The ethylene-a-olefin copolymers which are produced following theteachings of the prior art have been found to be random with respect tothe comonomer distribution within the copolymer molecule butheterogeneous with respect to the copolymer distribution betweenmolecules of the copolymer. g

It is an object of the present invention to provide a process for thepreparation of ethylene-a-olefin copolymers under continuous processconditions using catalyst systems and process variables so chosen thatthe copolymers produced have a narrow molecular weight distribution, arandom distribution of comonomer units along the polymer backbone andare homogeneous between molecules with respect to their comonomercontent.

A further object is the provision of ethylene copolymers with improvedphysical properties, said ethylene copolymers being the copolymerizationproduct of ethylene and at least one other u-olefin, at least one suchother a-olefin having four or more carbon atoms.

Accordingly, the present invention comprises a continuous process forthe preparation of homogeneous random partly crystalline copolymers ofnarrow molecular weight distribution comprising ethylene and at leastone other u-olefin, at least one such other a-olefin having four or morecarbon atoms comprising the steps of polymerizing the monomers dissolvedin an inert nonpolymerizable solvent therefor and for the copolymer tobe prepared in an I agitated reaction zone maintained at a pressuresufiicient to maintain the monomers in solution and at a temperature of40 to 110 C. in the presence of a catalyst prepared by mixing (A) anorganoaluminum halide R AlX- wherein R is an alkyl or aryl radical, n isnot greater than 1.5 or less than 1.0 and X is C1 or Br and (B) avanadium compound selected from (1) VO(OR) X Where R is an alkyl or arylradical, m is not less than 1 or more than 3, and X is C1 or Br and (2)vanadium oxyhalides soluble in the reaction medium; provided that whenthe vanadium compound is selected from (1) the vanadium concentration inthe reaction zone is not greater than 0.260 millimole/liter of solutionand the Al/ V ratio in the reaction zone is not less than /1 when thea-olefin is a C or C u-olefin, not less than 9/ 1 when the a-olefin is aC to C a-olefin and not less than 12/1 when the a-olefin is a C to Ca-olefin, and that when the vanadium compound is selected from (2) thevanadium concentration in the reactor is not greater than 0.160millimole/liter of solution and the Al/V ratio in the reaction zone isnot less than 5/1 when the a-olefin is a C to C m-olefin.

The present invention also comprises a copolymer of ethylene and atleast one other tit-Olefin, at least one such other a-olefin having fouror more carbon atoms, said copolymer being characterized by a narrowmolecular weight distribution and a homogeneity index, as definedhereinafter, of at least 75.

The inert solvent used as a reaction medium may be an aliphatic,aromatic or cycloaliphatic hydrocarbon, such as heptane, toluene orcyclohexane. The solvent chosen must be a solvent for the monomer andfor the polymer produced in the reaction. Cyclohexane is the preferredreaction medium.

Suitable u-olefins for use in practicing the process of the a presentinvention are u-olefins having at least four carbon atoms, such as, forexample, l-butene, l-hexene, l-octene, :or l-octadecene. Preferreda-olefins are l-butene and loctene. When the vanadium compound, used inpreparing -the catalyst, is an oxyhalide, the comonomer should notcontain more than 9 carbon atoms.

When practicing the process of the present invention, the reaction zoneshould be maintained substantially free of concentration gradients. Thismay be accomplished by v FIG. III is a graph representing therelationship between copolymer melt index and density difierence frominelt index 1.0.

In FIG. I, lines A and B show the relationship between the crystallinemelting point and comonomer content for various ethylene-a-olefincopolymers where the oc-Olfififl is 5C Specifically, line A is a plot ofEquation 1 below which is a computer generated equation based onregression analysis of the melting point-comonomer content data for aseries of commercially available heterogeneous ethylene-butenecopolymers and experimental heterogeneous ethylene-octene copolymers.

Equation 1 t I Copolymer melting point C. v v

Since heterogeneity is a relative rather thanabsolu'te'term, it isobvious that no single melting point vs. comonomer content relationshipcan be defined for all heterogeneous copolymers.

Line B of FIG. I is a plot of Equation 2, a computer generatedrelationship based on regression: analysis of the meltingpoint-comonomer content data for copolymers prepared under the preferredconditions of thepresent invention (runs 11-28, Table II).

Equation 2 Copolymer melting point C.

It is evident, from FIG. I, that copolymers which are not homogeneous incomonomer content show fc'ry's talline melting points at a givencomonomer content which are significantly higher than the melting pointsofjhomogeheous copolymers of the same comonomer content., 'Horn ogeneous-random ethylene-a-olefin copolymers (wlieiethe a-olefin is ;Care defined therefore as those copolymers whose crystalline meltingpoint is .related to their.comonomer content by Equation 2. Copolymerswith-melting points greater than that predicted lay-Equation 2.-areheterogeneous to the extent that their melting pointe'xceeds the valuegiven by Equation 2. If=this melting .point is elevated by comonomerheterogeneity to the point where it exceeds the value predicted byEquation 3 below,:the copolymer is considered suliiciently heterogeneousto fall outside the specific embodiment of-the present invention.

Equation 3 Copolymer melting p0int. C, i i

=Bil-15.77 orig/iooo-tvinyliiooc i +0.818(CH /C+viny1/100C;)

density difference is a useful index of copolymer homogeneity.

The following examples will help to illustrate the present invention:

Several runs were made using a well agitated continuous reactor systemoperating under essentially turbulent mixing conditions such that aconstant environment, substantially free of concentration gradients, wasmaintained in the reactor. Ethylene, the desired u-olefin or a-olefins,the catalyst components and hydrogen if desired for melt index controlwere dissolved in the inert solvent and fed into the reactor, which wasmaintained under varying pressures, for varying contact times. Theprocess conditions and the results of these runs were tabulated inTables I-VIII which follow.

Polymer properties referred to hereinafter in the tables were determinedby the following methods.

MELT INDEX ASTM Dl 23 8.

STRESS EXPONENT 1 S.E.== (log MELTING POINT wt. extruded with 6480 g.wt.) wt. extruded with 2160 g. wt.

The differential thermal analysis determination of melting point wasmade using a Perkin-Elmer differential scanning calorimeter (DSC)calibrated for temperature with indium metal and flushed with drynitrogen gas at a flow rate of 40 mls./min.

The samples were in the form of discs A" in diameter, 3 to 4 mils thickand about 2 mg. in weight. Prior to the melting point determination, thesamples were heated to 180 C. in the DSC apparatus, held there for 5minutes and then cooled at a rate of C./min. to C. The

melting points were determined on the subsequent melting profilesobtained at a heating rate of 20 C./ min. The melting point was taken asthe peak of the highest melting endotherm. Homogeneous copolymers werecharacterized by a sharp melting endotherm. Increased copolymerheterogeneity tended to broaden the melting endotherm as well as toraise the temperature at which the endotherm occurred.

Since the melting point data on polymer systems are critically dependenton annealing conditions, it is essential that the samples be put throughthe same melting-cooling cycle prior to melting point determination.

COMONOMER ANALYSIS 7 The determination of total alkyl groups was made bythe ASTM method Tentative Method of Test for Alkyl Groups inPolyethylenes based on Infrared Spectrophotometry-Proposed Revision ofD223 864T using method -A1Standard Sample Compensation Method K1 foralkyl groups greater than C was taken to be 0.110;

K' for ethyl groups was taken to be 0.074 and the factor h obtained bycalibration with cetane, was determined to be 141.5. The total number ofalkyl groups was determined and reported in terms of total methyl groupsper carbon atoms.

The number of side chain methyl groups was obtained by subtracting thenumber of terminal methyl groups from the total number of methyl groups.The number of terminal methyl groups was calculated from the followingformula:

No. of terminal methyl groups=V +2Vd+2T where V=number of vinylgroups/100 carbon atoms Vd number of vinylidene groups/100 carbon atomsT=number of trans groups/100 carbon atoms.

The concentration of vinyl, vinylidene and trans unsaturation groups inthe copolymers was determined by infrared spectrophotometric absorbancesat 908, 889 and 965 cm. using molar extinction coefficients of 121.0;103.4 and 85.4 respectively.

For normal alkyl groups the number of side chain methyl groups alsorepresents the number of branches and is related directly to thecomonomer content of the copolymers.

COPOLYMER DENSITY Copolymer density was determined by ASTM MethodD1505-63T. Since copolymer density is related to both comonomer contentand copolymer molecular weight (or melt index), the observed density wascorrected to melt index 1.0 using the relationship given in FIG. III.

HOMOGENEITY INDEX Equation 4 17112100 7.42(CH3)+0.414(CH -MP 1 whereHI=homogeneity index CH :total CH /100C+vinyl/ 100C MP =melting point ofcopolymer.

It should be noted that only homogeneous copolymers of ethylene anda-olefins of at least four carbon atoms follow the melting pointrelationship of Equation 2 or line B of FIG. I. The determination ofhomogeneity index is not applicable, therefore, to terpolymers wherepropylene is one of the comonomers.

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3,645,992 11 12 I w r Runs land 2 in Table Iillustrate the copolymerizaton TABLE V EFFECT F ALKyL/ALUMlN UM RATIO 0N of ethylene with l-buteneand l-octene respectively using COPOLYMER HOMO GENEITY coordinationcatalysts and reaction conditions of the prior Run number 40 41 art. Theheterogeneous ethylene/l-butene copolymer of Run 1 shows a relationshipbetween crystalline melting gthylene Feed (g-kmnute) 0257 0257' pointand comonomer content which falls on line A of omonomer 1-butene-....-.l-octenc. go mon one rlr ed g j/mmute) 3. 15;

FIG. I and between copolymer density and cornonomer oven 111.111.111.118a 1 v --tss 039 232 2252 3352 232 ifiotifififiii ihiiti ifi a a ys 3 -n-3 I I n I u n oocatalystlcatalyst mic 14A 10 llar relationship betweencrystalline melting po nt and c0 catallysltl confentrate in reactor mnn-0 099 O 126 monomer content and between copolymer density and c0- zno esiter Reactor temperature, C 100 100. mone'mer content Reactor contacttime (minutes)-- 2.68 2.07. Runs 3 to 10 of Table I illustrate thecopoiymerization 6Ziififiiiiiiismrr;1:11:1; giiiiitiiiiiiiii: if; ofethylene with l-butene 3, 4, 5, 6 and and with Copolymer stress exponent1.33 l-octene (runs 7, 8 and 10) using synthesis conditions andgggggggg; gggigg e gg g5 lyst formulations recommended by the prior artfor 0.9210 0.9318. the preparation of ethylene/propylene copolymers. TheQE QJZJQJSELFFTEQQ ff f f L32 1m p y s p d in Runs 3 to 10 are similarto the Copoiymer side chain omgiooc 1.20 1.10. heterogeneous copolymersof Runs 1 and 2 as shown by %gg$ g ffffi g' comparison of thecrystalline melting point and/ or density Hydrogen (micromoies/minute)23.1"... 20.4. of these copolymers (as a function of their comonomerCatalyst formation conditions In situ In situ.

content). It is apparent that the coordination catalysts systerns ofRuns 3 to 10 offer little or no improvement over the standardcoordination catalysts of Runs 1 and 2.

TABLE VL-EFFECT OF AlfV RATIO ON COPOLYMER HOMOGENEITY Run Number 42 4344 45 4 4 Ethylene feed (g./minute)..--- 0.257 0.257 0.257 0.257Comonomer 1-butene l-octene- Comonomer feed (gJminute)- 0.099 0.257..--Solvent (mL/minute) 13.33 13.56 Cocatalyst (Ethyl)AlCl (Ethyl)AlClCatalyst O(O-n-butyl)3.-. VO(O-n butyl)3- Cocatalyst/catalyst ratio 5.18.8. Catalyst concentration in 0.142 0.

reactor (millimoles/liter). Reactor temperature, C 100 100 100 100i 100100.

Reactor contact time (minutes)- 2.98.-. Ethylene conversion 0.712-Copoiymer melt index (M.I.). 1.47.

Copolymer stress exponent. 1.38. Copolymer density 09210-. Copolymerdensity (cor- 0.9200

rected to M.l.. 1.0. Copolymer total GHQ/100C 1.28 1.30 1.34 1.390.76.---

and vinyl unsaturation. Cgpolymer side chain CH3] 1.19 1.29Copolymermelting point,C-- 100.8 108.9 106.8, 110.8 106.8, 112.6, 117.3Homogeneity index 85.- S0. 71 Hydrogen (micromoles/ 5.3 21.8

minute Catalyst formation conditions- In situ In situ In situ In situ.

TABLE VII-EFFECT OF VANADIUM CONCENTRATION ON COPOLYMER HOMOGENEITY Runnumber 48 49 50 51 52 53 54 Ethylene feed (g./minute).---- 0.257 0.2570.257...- 0.257 0.257. Comonomer l-hutene l-butcne l-octene Loctcne.Oomonomer feed (g./minnte) 0.0808 0.047 0257-.- 0.259. Solvent(ml/minute) 12.88 12.69.. 12.16 13.48. Cocatelyst (Ethyl) A101 (Ethyl)AlC (EthyDAlCh (Eth 1)A1C1,. Catalyst VOC a..-. VOC a- VO(O-n-butyl) C.-VO((-n-butyl);0l. Cocatalyst/catalyst ratio 14.1. 15.2. 14.4 15.4.

atalyst concentration in 0.538. 0.261 546 0 252. reactor(millimoies/liter). Reactor tempcrature,.0 100.. 100.. 100. 100. Reactorcontact time 3.09. 3.13. 3 ll 3.16 3.25 3.26 2.94

(minutes). Ethyleneconversionu 0.722. 0.720 0.512 0605 0.445 0650 0 572.Copolyxner melt index 17.4. 1.52--- 0.75..- Copolymer stress exponentCopolymer density 0.9250- 0.9277-.- 0.9230- (lgpcilayinelr density(corrected 0.9105 0.9267 0.9239 0.9280 0.9223 0.9179 0.0200

- 0 Copolymer total (3113/1000 1.46 0.96 1.20 1.40 1.02

and vinyl unsaturation. Citiggicymer side chain 0113/ 1.33 0.87 1.151.26 0.91 1.33 1.08. Copolymer melting point, C- 109.9 114.4 100.6101.12, 115.1, 112.6.--. 109.6 109.2.

- I 8.8. Homogeneity index. 66

Hydrogen (m ctornolesi nu Cataiyst formation conditions. In situ in situIn situ In situ In situ In situ In situ.

comonomer, di-n-butyl chlorovanadate (Run 53) produces a significantlymore homogeneous copolymer than does VOCl (Run 51). Even under optimumconditions, VOCl yields a heterogeneous copolymer with l-octadecene (Run30) while VO(O-n-butyl) yields a homo geneous l-octadecene copolymerunder otherwise identical conditions (Run 19).

The present invention is also applicable to interpolymers processvariable defining the area in which homogeneous copolymers can beprepared pertain only when the other defining process variables are ator near their optimum value for homogeneous copolymerization. i

The ethylene/l-butene copolymer produced in Run .1 using a prior artcoordination catalyst was subjected to fractionation and the resultstabulated in the following table.

TABLE IX Copolymer fractionation data:

copolymer No. Run 1, Table I V i 7 Melt IIldBX-2-85 Density-0.9220

[Amount fractionated-10.0 grams, percent recovery-97.12]

Fractionation- Weight 1 Corrected Cumuaverage Side fraction lativeInhermolecular H chain DSC weight weight ent visweight CH3] melting(grams) percent cosity Mw 10- 1 y 100 C 7 point Fraction N0.:

Refractionatlon- 1 0. 371 98. 32 5. 22 320 0. 77 2- 0. 246 95. 24 3. 68190 1. 09 3 0. 757 90. 22 2. 94 145 1. 27 4 0. 578 83. 55 2. 29 105 1.21 0. 334 78. 99 1. 93 84 1.48 .1 6. 0. 581 74. 41 1. 62 66 1. 60 117. 07. 0. 410 69. 46 1. 37 52 1. 72 8. 0. 479 56. 01 1. 18 44 1. 91 9. 0.204 61. 60 1. 14 0. 171 59. 72 0. 92 11 0. 414 56. 80 0. 77 Wholepolymer 1. 37

1 Used in refractionation.

of ethylene and more than one u-olefin when at least one of thea-olefins contains four or more carbon atoms. Examples are theethylene-octene-butene terpolymer of Run 55 and theethylene-octene-propylene terpolymer of Run 56, Table VIII. Theseterpolymers are of practical interest because their physical propertiesare nearly equivalent to the corresponding octene copolymers and yetthey contain considerably less of the high cost octene comonomer.

It should be noted that the limits of any individual TABLEX Copolymerfractionation data:

Copolymer No. Run 3, Table I Melt Index2.21

Density0.9206 [Amount fractionated-10.0 grams, percent recovery-95.01]

Fractionationfi P I V Veigh t 5 Corrected Cumuaverage "f S1de -DSOfraction lative Inhermolecular chain. melt- Weight weight ent visweightCHa/ ing (grams) percent" cosity M, a. 1000 point Fraction No.: I

1 Used in reiractiouation.

' Ethylene feed (gJminutc) TABLE VIlI.-HOMOGENEOUS TERPOLYMERS 0.257Comonomer 1-butene l-octene. l-octcne- Propylene.

Comonomer feed (g/minute) 0.0658- 0.0974 0.0974- 0.0488. Solvent(ml/minute) 13.29 13.67 Oocatalyst (Ethyl) A101 (Ethyl) AlCl; 1 CatalystVO (O-n-butylh VO (Oh-butyl);

Cocatalyst/catalyst ratio 14.7 15.0 Catalyst concentration in reactor(mlllimoles/liter) 0.127 0.119 Reactor temperature, C 100 100 Reactorcontact time (minutes) 3,00 2.91 Ethylene conversion 0.603 0.680Copolymer melt index (M.1.) 1.27 3.10 Copolymer stress exponent- 1.161.15 Copolymer density 0.9223 0.91.73 Copolymer density (corrected toM1. 1.0)- 0.9217 0.9147 Copolymer total GHQ/1000 and vinyl unsaturatlon43 0.91 1 9 H 1 1 exy exy oopo ymer s de cha n 0 3. 0- EthyLfi MethylCopoly-mer melting point, C 111.3 105.8 Homogeneity index 12 .Hydrogen(micromoles/minute) N11 N 11 5' Catalyst formation conditions- In s1tuIn situ 1 Estimated from comonomcr reactivity data Runs 11 to 28illustrate the copolymerization of ethylene w ith l-butene, l-octene andl-octadecene using reaction conditions equivalent to those used in Runs3 to except for the reactor temperature and the composition andconcentration of the catalyst systems used. The copolymers produced showcrystalline melting points which are sharp and well, defined. Regressionanalysis of these data gave the relationship between methyl point andcomonorner content as shown in Equation 2 and plotted as line B in FIG.;I."The lower crystalline melting point of these copolymers incomparison with the heterogeneous copolymers of line A of FIG. Iindicates the difference in structure between the two types ofcopolymers. Furthermore, it indicates that. the lower melting copolymerscontain less of the longer ethylene sequences (at a given comonomercontent) than the higher melting counterparts and have a morehomogeneous overall comonomer distribution.

, Typical catalysts for copolymerization of ethylene and propyle'ne torubber-like copolymers based on alkyl aluminimum halides and vanadiumderivatives fail to produce partly crystalline homogeneous it-olefincopolymers under solution process conditions due to a combination ofprocess and catalyst variables.

, A comparison of the results of Runs 29 and 30 indicates catalystsystemjn general, it is observed that the catalysts *which are suitablefor the copolymerization of higher 0:- flolcfins are'r'norejlimited thanthose suitable for copolymerization of the lower-a-olefins.

Runs33 and -34 illustrate the efiect of increasing the reactortemperature in the copolymerization of ethylene .WflhIll-liutene usingan} (ethyl)AlCl VO(O-n-butyl) 3 'catalys ,system; At reactortemperaturesabove 130 C., the. buteneicopolymer crystalline melting point increasesat a gi-ven co rnonomer content indicating an increase in copolymerheterogeneity. Runs 37 to 39 illustrate the eflFect 'of temperature onoctene copolymer homogeneity using the catalyst system (ethyl) AlCl'VOCl and runs 35, 36' show the same effect with the (ethyD1.5AlCl-VO(O-n-decylhCl catalyst system. These data show that the maximumreactor temperature for the synthesis of octene copolymers .llnuiinolarmixture of enl n naci and (ethyDAlCls.

of homogeneity index is in the range to C., although the temperature maybe slightly higher for the synthesis of butene copolymers.

Runs 40 to 41, Table V, illustrate the low copolymer homogeneityobtained when R AlCl is used as alkylating agent rather than R AlCl (Run13, Table II) or RAlCl (Run 14, Table II). This pronounced change incopolyrner homogeneity between an alkyl/ aluminum ratio of 1.5 and analkyl/ aluminum ratio of 2 was totally unexpected based on the priorart.

Runs 42 to 45, Table VI, illustrate the effect of the ratio of the alkylaluminum halide to the vanadium compound VO(O-n-butyl) on butenecopolymer homogeneity (Run 42) and on octene copolymer homogeneity (Runs43 to 45). For VO(OR),,X based catalyst systems where 1121 the minimumAl/ V ratio is dependent on the particular comonomer used. Long chainm-olefins such as loctene, require a higher Al/ V ratio than shorterchain orolefins, such as l-butene. The data indicate that a minimum Al/V ratio of about 5/1 for butene copolymers must be maintained in thereactor and that the minimum Al/ V ratio for octene copolymers is about9/1. For 0t-O1CfiI1S of C to C 0, an Al/ V ratio of at least 12/1 shouldbe maintained in the reactor.

With VOCl based catalyst systems, on the other hand, an Al/V ratio of 55is suitable for homogeneous copolymerization of either butene (Run 46,Table VI) or octene (Run 47, Table VI) but l-octadecene cannot behomogeneously copolymerized with this catalyst system even at high Al/ Vratios (Run 30', Table 111) Runs 48 to 54, Table VII, illustrate theeflfect of vanadium concentration in the reactor on copolymerhomogencity. The results indicate that in order to obtain homogeneousoctene copolymer, the vanadium concentration should not exceed about0.16 mmole/litre for systems based on VOCI (Runs 51 and 52) and about0.260 mmole/litre for systems based on VO(0R) Cl (Runs 53 and 54). Thecatalyst concentration elfect is less pronounced with shorter chaina-olefins, such as l-butene, but Runs 48 to 50 indicate that with VOClthe highest level of homogeneity is obtained at catalyst concentrationsbelow about 0.260 mmole/litre.

The eliect of the chemical structure of the vanadium compound oncopolymer homogeneity is intimately related to a-olefin comonomer size,vanadium concentration in the reactor, reactor temperature, Al/V ratioand R/Al ratio in the alkyl aluminum halide. When the other variablesaffecting comonomer distribution are not adjusted to optimum valuestrialkyl vanadates and dialkyl chlorovanadates show a reduced tendencyto heterogeneous copolymerization in comparison with VOCl or VCl Acomparison of Runs 51 and 53, Table VII, shows that, at high vanadiumconcentrations using l-octene as DSC melting point Similarly, theethylene/l-octene copolymer produced in Run 8 using catalystformulations recommended for ethylene/propylene rubbers was subjected tofractionation and found to be heterogeneous, as shown by the followingtable.

TABLE XI Copolymer fractionation data:

Copolymer N0. Run 8, Table I Octene Copolymer Melt Index-1.20.

[Density-0.9347, amount fractionated-10.0 grams, percent recovery 96. 8]

Fractionation- Corrected Cumufraction lative Inherweight weight; entvis- (grams) percent cosity Mw 1O is o 17 comonomer di ribution of thewhole copolymer must be considerably broader than the copolymer analysthe fractions would indicate.

The ethylene/l-butene copolymer produced in Run 3 using a coordinationcatalyst system recommended for 5 ethylene/ propylene rubbers, wassubjected to fractionation and the results are tabulated in Table X,above.

The copolymer is heterogeneous and shows no improvement over theethylene/l-butene copolymers prepared in Run 1.

1 Used in refractionatlon.

The results show that all the molecular weight fractions containequivalent amounts of comonomer.

A homogeneous, random ethylene/ l-butene copolymer prepared according tothe process of the present invention was extruded in blown film form.The properties of this film were then compared with the properties ofiiilm prepared from conventional ethylene/l-butene copolymer. Theresults of the comparisons are tabulated in the following tables.

TABLE Kill-PHYSICAL PROPERTIES OF BLOWN COPOLY- MER FILM 1 Homogeneous-Heterogeneousrandom random butene butene Copolymer type copolymercopolymer Copolymer:

Melt index 1. 94 1. 62 Stress exponent 1. 22 1. 31 Density H 0. 9189 0.9190 Film properties:

Elastic modulus:

45 8 Inside 47 Tensiles MD:

Elongation, percent 725 825 Yield strength, psi 1, 600 1, 650 Ultimatebreaking strength,

p.s.i 4, 4:00 4, 400 Tenslles TD:

Elongation, percent 750 900 Yield strength psi 1, 600 1, 600 Ultimatebreaking strength,

p.s.i 4, 350 4, 100 Gauge, mils 2. 46 2. 45 Impact strength, 26" darttest 139 109 l Extruder type 2 Boyle, die gap 25 mils.

tain the monomers in solution and at a temperature of to 100 C. in thepresence ofa catalyst prepared by mixing (A) an organo-aluminnm halideR,,AlX-, wherein R is an alkyl or aryl radical, n. is not greater than1.5 or less than 1.0 and X is C1 or Br and (B) a vanadium compoundselected from (1) VO(OR) X where R is an alkyl or aryl radical, m is notless than 1 or more than 3, and X is C1 or Br and (2) vanadiumoxyhalides soluble in the reaction medium; provided that when thevanadium compound is selected from (1) the vanadium concentration in thereaction zone is not greater than 0.260 millimoles/liter of solution andthe Al/V ratio in the reaction zone is not less than 5/1 when the alphaolefin is a C or C alpha-olefin, not less than 9/1 when the alpha-olefinis a C to C alpha-olefin and not less than 12/1 when the alpha-olefin isa C to C alphaolefin, and that when the vanadium compound is selectedfrom (2) the vanadium concentration in the reactor is not greater than0.160 millimoles/liter of solution and the Al/V ratio in the reactionzone is not less than 5/1 when the alpha-olefin is a C to Calpha-olefin.

2. The process according to claim 1 wherein the (IL-Olefin is l-butene.

3. The process according to claim 2 wherein catalyst component (A) is(ethylh AlCl and catalyst component (B) is VO(O'-n-butyl) Ci and theAl/V ratio in the reaction zone is about 5/1 to about 10/1.

4. The process according to claim 2 wherein catalyst component (A) is(ethyl) AlCl and catalyst component (B) is VOCland the Al/V ratio in thereaction zone is about 5/1 to about 10/ l.

5. The process according to claim 1 wherein the a-olefin is l-octene.

TABLE XIV-PEAR STRENGTHS 0F EXTRUDED FLAT FILM Film Elmendorf tearthickstrength 'lD/MD Extrusion ness tear Gopoiymer draw ratio (mils) TDMD ratio 14. 5 1. 17 370 290 1. 3 Homogeneous-random oetene eopolymer:melt index, 2.2, density, 0.9195 g g; 9. 2 1.85 350 197 1. 8Heterogeneousrandom oetene copoly- 13.4 1. 27 443 156 2. 8 met: meltindex, 1.8, density, 0.9185..- 17.0 1.00 577 124 4. 6 28.4 0. 60 658 729.1

Film extruded on small Instron mounted ram extruder.

The copolymers of the present invention are of practical importancebecause of the effect of the homogeneous comouomer distribution andnarrow molecular distribution on their physical and optical properties.Films of these copolymers show a reduced haze level, higher impactstrength, reduced tendency towards delamination, and a better balance ofphysical properties in the machine and transverse directions.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Continuous process for the preparation of homogeneous random partlycrystalline copolymers of narrow molecular weight distribution, saidcopolymers having a homogeneity index of at least 75 as determined bythe equation:

130-7.42 (CHa) +0.414(CH MP HI= 11.090113-0.55%(CH3) where HI equalshomogeneity index CH =Total OHg/lOOC-i-ViHYl/ 100C MP =melting point ofthe copolymer,

6. The process according to claim 5 wherein catalyst component (A) is(ethyl) AlCl and catalyst component (B) is VO(O-n-butyl) Cl and the Al/Vratio in the reaction zone is about 9/1 to about 15/ l.

7. The process according to claim 5 wherein catalyst component (A) is(ethyl) AlCl and catalyst component (B) is VOCl and the Al/V ratio inthe reaction zone is about 5/1 to about 10/1.

8. The process according to claim 1 wherein the ot-olefin comprises amixture of l-butene and l-octene.

9. The process according to claim 8 wherein catalyst component (A) is(ethyl) AlCl and catalyst component (B) is VO(O-n-butyl) Cl and the Al/Vratio in the reaction zone is about 9/ 1 to about 15/1.

10. The process according to claim 8 wherein catalyst component (A) is(ethyl) AlCl and catalyst component (B) is VOCland the Al/V ratio in thereaction zone is about 5/1 to about 10/ 1.

11. A process according to claim 1 in which the homogeneous randompartly crystalline copolymer has a homogeneity index in excess of 90.

12. A process according to claim 6 in which the homogeneous randompartly crystalline copolymer has a homogeneity index in excess of 90.

13; A process according to claim 10 in which the homogeneous randompartly crystalline copolymer has a homogeneity index in excess of 90.

(R f rences on following page) 3,645,992 7 21 22 References Cited OTHERREFERENCES UNITED STATES PATENTS Copolymerization, edited by George E.Ham, High Polymers, volume XVIII, Interscience Publishers, a div.

12/1962 cines of John Wiley and Sons, New York, 1962, 116 11 2/1967Hagemeyer 260-882 5 JOSEPH L. SCHOFER, Primary Examiner 3/1969 Nana260*93] R. s. BENJAMIN, Assistant Examiner FOREIGN PATENTS Us. CLX'R3/1967 Great Britain. 10 26088.2 R & F

